Questionnaire sorting is a concept for sorting mentioned by Coxon [(1999) SORTING DATA. Collection and Analysis. Thousand Oaks: Sage] and Harloff and Coxon [(2005), How to Sort. A Short Guide on Sorting Investigations. www.methodofsorting.com]. The use of questionnaire sorting is detailed herein. A paper questionnaire variant and a HTML form variant are introduced. Their equivalence among each other and with traditional sorting of paper cards is tested for two sets of items. These sets consist of 20 colors and 25 web-site content items. Results from paper questionnaires and HTML forms do not differ significantly. Contradictory results were obtained on the equivalence of paper card sorting and questionnaire sorting, depending on the item sets. Another variant allowing for placement of items in several clusters simultaneously has been termed fuzzy sorting (Harloff and Coxon, 2005, How to Sort. A Short Guide on Sorting Investigations. www.methodofsorting.com). Its first detailed application is given here for both paper card sorting and questionnaire sorting. The difference between results from fuzzy sorting and partition sorting experiments was tested using paired t-tests. The type I error is below 0.01. In contrast to current practice it is therefore advisable to use instructions and a mathematical model for sorting fitting to the methods of subsequent statistical analysis and to the designed domain. Results from two fuzzy sorting experiments are analyzed by fuzzy cluster analysis and network analysis, respectively. Fuzzy sorting and fuzzy cluster analysis provide much more detailed information than the common partition sorting and hierarchical cluster analysis. Network analysis gives valuable information about facet structure.